From my experience with both sticks & staples, the waste tank solutions primarily try to mask the odor.

When I built my bus system I used 2" vent and revent all around.

I went on a trip in January and did not empty the tank. It wasn't until I was working on the roof a couple of weeks ago that I smelled the odor out of the roof vent. Good venting works. Never a smell inside.

On the additive issue:I did some recent research on septic tanks recently and the generally accepted answer is the only thing you need to add is human waste and water. It will supply all the bacteria you need. Some of the solutions may speed it up, but if you smell wintergreen, roses, whatever, it is still really the masked odor of waste

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1975 GMC P8M4905A-1160 North Central Florida

"There are basically two types of people. People who accomplish things, and people who claim to have accomplished things. The first group is less crowded." Mark Twain

I have not tried this but someone on one of the boards gave this link. Once we get going in our bus, I'm going to try it. It seems logical. It's called the GEO method: http://home.mindspring.com/~cbruni/index.html-BrentEagle 10

My experience agrees with Fred and Floridacracker. All I have is good 2" venting, a good toilet seal, and never any smells, under any conditions. I typcially go months between dumping. I don't think any of the additives do any good, and the ones that killl bacteria actually harm any tank you dump it in, while not really providing an odor free tank.

My home is on septic system, and every septic person I have ever talked to agrees that the only thing it needs is regular additions of water and human waste. Human waste has all the bacteria that is required for good breakdown of solids.

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Jim StewartEl Cajon, Ca. (San Diego area)

Travel is more than the seeing of sights, it is a change that goes on, deep and permanent, in the ideas of living.

I've tried Yeast, like you buy in the bakeing section of the store. If you are dumping in the boonies, It does seem to help the digestive process. But like others have said a well designed system is best. If you are getting oders there are other ways to tackle the problem. Work?/Play safely Jim

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Remember, even at a Mensa convention someone is the dumbest person in the room!

Several folks replied to that post (and to this one as well) that they did not use anything. I am not quite ready to take that approach just yet. On our maiden trip, we used some generic septic tank treatment and it did not seem to do a very good job. Towards the end of the trip we picked up some Ridex and that seemed to really help.

As was noted earlier, the tank vent is very important. I plumbed a 2 inch vent and then capped it off with the typical RV vent cap. When we went down the road, the smell about killed us. When we got back, I removed the RV cap and put a "sweeping" 2 inch Tee on. I then went on a short trip and there was no smell. The tank has not been dumped in over two weeks. I suspect the major factor is the new "cap".

Unless your tank was completely full, I suspect that you have an air leak from the holding tank back into the coach such as shower trap, Kitchen or bathroom sink trap, Dishwasher or clothes dryer trap, bad toilet seal or something like that. I had a standard cap on my vent and the only time I got odors was caused by one of the above. Richard

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Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body. But rather to skid in sideways, chocolate in one hand, a good Reisling in the other, body thoroughly used up, totally worn out and screaming: WOO HOO, what a ride

We've been having problems with sewer smell, also. I vented my tanks through the roof midway and used a venturi vent.

What I think I've narrowed it down to is the seal on the roof hatch. I can feel it drafting air INTO the coach when cruising down the road. What I think is happening, is the venturi vent (which is just in front of the hatch about 3 feet) is pulling gases out of the tank, and then they are getting sucked back into the coach through the leaking seal on the roof hatch.

I'm going to relocate the vent towards the rear of the bus, behind the hatch.

I also tied my battery vent into the tank vent before exiting through the roof. I could not convince myself it would be a problem with pulling battery gases into the coach. Unfortunately, I only looked at the problem from the one side. I realized that when I turned on the air conditioner blower which created a vacuum in the poorly sealed compartment where the batteries are located. You can guess the rest.

So, my plan now is to put a new vent in the rear for the black tank vent, and use the current vent for the batteries.

You can do a "smoke test" on your system. You go to your local plumbing supply store (not home depot or Lowes) and buy a smoke bomb they come in different cubic footages a small one will do, but buy 2. you then seal all openings with duct tape or whatever you have handy, including the overflows in toilet and sink, shower drain, sink's ect. also tape off the vent on the roof. Get your shop vac and some pvc fittings 1in or larger will do. Make a tee that you can tap into the system, be creative here, you can take off a sink trap, use a cleanout plug, I have a 3" access plug on my black water tank that I used. The bottom part of the tee is going to be capped off. One end is going to be inserted into your system a lighted smoke bomb is going to be put in the capped off part of the tee and a shop vac with the hose put in the exhaust port is put on the other end of the tee. What you are trying to accomplish here is to pressurize the system with smoke in it, the smoke will pinpoint your leak. Work?/Play safely Jim

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Remember, even at a Mensa convention someone is the dumbest person in the room!

This probably doesn't pertain but I have read a lot of guys venting thier systems upward towards the roof and having problems like odors coming into the coach. I vented mine simply by using a 2 inch pvc pipe coming out of the top side of my round tank and going directly downward thru the bay floor and then rearward with a baloney cut on the end. It only goes about 6 or so inches under the bay floor. I have never had a problem with odors of any kind while stationary or moving!

This may be a little abstract, but is it possible that your venturi cap is pulling the water out of the sink and shower traps? That would allow all sorts of odors back into the coach. If your vent is t'eed between black and grey, the blackwater and grey gasses will mix and may be "pumping" back through a sink or shower. I've got a two inch vertical vent that is between the hatch in the bedroom and the bath Fantastic Fan Vent and have not had any problem at all when using standard RV tank treatment. I'm using a round RV cap on mine...it doesn't "draw" a vacuum on the system when moving...just vents.Have you looked for leaks around the pottie? That will make some stink when moving. The flange may be venting. You shouldn't have enough stink from the stack to cause a problem no matter the condition of the hatch seal. You'll have those vents open during nice weather. What are you using to treat the tanks? RV stuff works well. Not treating the tanks at all is garunteed to make a big stink that will be will be noticed by you and your neighbors. Your cleaning out the tanks after each use? Flush'em out and dump a little RV anti-stinkum and they should be good to go. Most of the RV treatments are environmentally friendly. Some of the trick is to keep the odors under control. Good luck, JR

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JR Lynch , Charlotte, NC87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.”